Spiraling behavior of photorefractive screening solitons

The question of spiraling or no spiraling of incoherent screening spatial solitons in photorefractive crystals is addressed by a careful numerical analysis. We find that the interaction of solitons typically results in an initial mutual rotation of their trajectories, followed by damped oscillations and the fusion of solitons. The rotation can be propelled to prolonged spiraling by the skewed launching of beams. This behavior is caused by the anisotropy of the refractive index change in the crystal.